Acoustic chamber



July 7, 1931. J. c. KARNES ACOUSTIC CHAMBER Filed Nov. 21, 1929 INVENTOR.

James E -Karnes TTORNEY.

Patented July 7, 1931 PATENT OFFICE JAMES C. KARNES, OF BUFFALO, NEW YORK ACOUSTIC CHAMBER Application filed November 21, 1929. Serial No. 408,840.

(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AMENDED APRIL 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

b This invention relates to an acoustic cham- An essential component of an anti-aircraft defense system consists of a corps of observers whose duty is to ascertain and report the location, number and type of hostile aircraft, the angle of approach and the altitude. This is a most diflicult assignment, especially under conditions of darkness and requires considerable and continuous practice to secure proficiency. At the present time such practice is conducted outdoors and necessitates that aircraft be sent aloft to provide a movable sound source. 7

Because of the fine distinctions which must go be made by aural deduction and comparison,

it is impossible to conduct the practices indoors with moving pictures and sound records because an auditorium suited to the purpose must have perfect acoustic properties.

In the design of auditoriums a compromise is usually effected between a maximum utilization of space and certain theoretical principles which have been found to control the conditions characterizing good acoustic propso erties. As a result of such compromises auditoriums have been constructed in which there are certain sections or areas where the sound is low in volume, indistinct or unnatural and in which vocal and instrumental 3; soundscan not be received with equal clarity. In providing sound accompaniment for motion pictures the number and distribution of the sound reproducers is controlled by the peculiarities of the particular hall in which they are installed. The proper arrangement is determined to afford clear reception over a maximum area of the auditorium which area may sometimes be increased by a profuse application of absorbent drapes.

In order to insure excellent acoustic properties for a hall it is proposed in the present invention to establish the auditorium in the form of a horn, preferably one having an exponential variation of cross section with the length. The auditorium is in prolongation of the stage which, in turn, is in prolongation of a sound reproducing horn.

l/Vith the foregoing and other objects in view, the invention resides in the novel arrangement and combination of parts and in the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed may be made within the scope of what is claimed without departing from the spirit of the invention.

A practical embodiment of the invention is illustrated in the accompanying drawings, wherein:

Fig. 1 is a floor plan of a hall constructed in accordance with the invention;

Fig. 2 is a schematic view in central longitudinal elevation thereof;

Figs. 3, 4 and 5 are views in end elevation looking towards the stage and showing different forms of ceilings.

Referring to the drawings by numerals of reference:

There is shown a building structure divided generally into an auditorium 5 and a stage 6. The floor 7 of the auditorium is sloped in accordance with standard practice to provide for tiers of seats 8. The side walls 9-9 and the ceiling 10 converge forwardly towards the stage and are flared and so curved outwardly as they approach the rear Wall 11 which is to be draped. The auditorium, therefore, is a gigantic horn and in the preferred embodiment, this horn is of exponential cross section, the form of the equation used in determining the design being A=A0e in which A is the cross sectional area at any point; A0 is the cross sectional area at the small end; 6 is the Naperian base; m is a constant determining the rate of flare; a: is the distance of A along the axis measured from the small end.

The particular shape of the auditorium in cross section may be determined from an architectural viewpoint. As shown in Fig. 3, the ceiling is arched; in Fig. 4 it is at right angles to the side walls and in Fig. 5 the side Walls and the ceilings are merged into an arch. V

The stage 6 is preferably a continuation of the auditorium having an exponential variation of cross section with the length. F or the presentation of motion pictures a screen 12 is placed on the stage.

. Sound reproducers may be placed on the stage at the rear or small end thereof'in the accustomed manner or a single sound reproducer horn 13 conforming to the design of the auditorium and stage may be provided, as shown in the drawings.

As a concession to the possible employ ment of an orchestra, a pit 14 may be provided directly in front of the stage. The presence of a pit and the fact that it may be desirable to extend the floor 7 below the level of the floor of the stage will cause an interruption in the conformity of the stage and auditorium at the extreme forward end of the latter but as this irregularity occurs on only one side of the horn and that the side having the large absorbing capacity'in the form of the audience no impairment in the transmission and reception of sound should be experienced. 7

Although preference has been expressed for an auditorium and stage having the form of an exponential horn, the one being in prolongation of the other, yet the invention contemplates and includes the separate formation as well as the associated relation of these chambers and the coordination of their four walls to form a horn.

\Vhile it has been common practice in the design of auditoriums to diverge the'side walls for the purpose of increasing the seating capacity, it is to be borne inmind that unless the ceiling is likewlse flared a sound transmitting horn is not represented.

In the exponential form shown in Fig. 1,

the auditorium is terminated when the side walls makean'a'ngle of approximately 45 With the axis or center aisle 15 of the chamber. This arrangement affords a maximum economical utilization of seating space and provides a side aisle 16 which increases in" width towards the exit 17 and will facilitate the exodus of the audience.

The principles setforth with regard to an auditorium and stage apply with equal aptitude to the formation of a chamber for sound recording or broadcasting. In such a chamher the sound source is originated at the large end or mouth and the recording instrument or the microphone is placed at the small end or throat.

I claim: v

1. In a building structure, an auditorium, having a floor, side walls and a ceiling cooperating to forma horn with an exponential variation of cross section with the length, a stage in prolongation of the auditorium, and a sound reproducer horn in prolongation of the stage.

2. In a building structure, an auditorium, having a floor,,side walls and a ceiling cooperating to form a horn with an exponential variation of cross section with the length and a stage in prolongation of the auditorlum.

3. In a building structure, an auditorium, having a floor, side walls and a ceiling cooperating to form a horn, a stage in prolongation of the auditorium, and a sound reproducer horn in prolongation of the stage.

4. In a building structure, an auditorium, having a floor, side walls and a ceiling cooperating to form a horn, and a stage in prolongation of the auditorium.

5. In a building structure, a stage having a floor, side walls, and a ceiling cooperating to form a horn with an exponential variation of cross section with the length, and a sound reproducer horn in prolongation of the stage.

6. Ina building structure, a stage having a floor, side walls, and a ceiling cooperating to form a horn, and a sound reproducer horn in prolongation of the stage.

7. In a building structure, a stage having a floor, side walls, and a ceiling cooperating to form a horn, with an exponential variation 7 of cross section with the length.

8. In a building structure, a. chamber having a floor, walls and ceiling cooperating to form a horn with an exponential variation; of cross section with the length. I

9. In a building structure, a chamber having a floor, walls and ceiling cooperating to form a horn having a generally increasing rate of change of cross-sectional area.

12. In a building structure, an auditorium.

having side walls and a ceiling diverging at a uniform rate.

13. In a building structure, an auditorium having a ceiling convex in the direction of its length, the curvature being the function of an exponential equation.

. 14. In a building structure, an auditorium having a ceiling sloping upwardly from stage end to rear and being convex in the direction of its length.

15. In a building structure, an auditorium having a ceiling sloping upwardly from stage end to rear.

JAMES C. KARNES.

10. In a building structure, an auditorium in theform of a horn having side walls and a ceiling diverging at a uniform rate and 

